Automatic damper



G. H. CROWBLL.

AUTOMATIC DAM-PER.

`Patented Jan. 1, 1889.

un em. lj C1 (o Model.)l

NiTEo STATES PATENT Erica.

GEORGE HEURY CROIYELL, OF BERLIN FALLS, NEV HAMPSHIRE.

AUTOMATIC DANI PER.

SPECFICATION' forming part of Letters Patent No. 395,382, dated Januaryl, 1889.

Application led April 4, 1888.

To all whom it may concern:

Beit known that I, GEORGE HENRY (taow- ELL, a citizen ofthe UnitedStates7 residing` at Berlin Falls, in the county ot' Coos and State ofNew .Ilampshire, have invented certain new and useful Improvements inAutomatic Damp ers; and I do declare the following to be a full, clear,and exact description of the invention, such as will' enable othersskilled in the art towhich it appertains to make and use the same,reference being had. to the accompanying' drawings, and to the lettersand figures of reference marked thereon, which form a part of thisspecification.

My invention relates to dampers, and more especially to that class knownvas automatic dampers,7 which are opened and shut by devices that aresensitive to the changes of temperature to which they are subjected.

My invention is applicable to all kinds of dampers, but is particularlyadapted for ovens. It is arranged in a suitable opening in the door orin the wall of the oven. As ordinarily constructed, these dampersoperate in connection with a stationary slotted basepiece or gridiron,the extent of opening being always the same for any given degree oftemperature. In my invention, however, I make the gridiron adjustable,and thereby am enabled to vary the extent to which the damper will openat any given temperature, ranging from wholly open to nearly or entirelyclosed.

In the drawings, Figure l is a front elevation of my device; and Fig. 2is a rear elevation, upside down from the position shownin Fig. l. Fig.is a liorizontal section, and Fig. 4f is a vertical section.

A is a shallow box or easing, deep enough to contain the sliding damperand the thermostatc devices. The front of the casing has one or morelslots, u, for the admission of air to the oven,V the easing beingfastened over an opening preferably in the oven-dom'. I have shown twoslots, a, in the drawings, though it is evident that the number may bevaried, as

desired. Inside the easing is an adjustable gridiron, B, consisting ot'a sheet of metal covering, the slots a, and provided with a series ofrectangular openings, l), opposite the slots a. The solid portionsbetween the openings Z9 are about one and one-half time as wide as theopenin gs themselves.

sei-in N0. 269,568. (No man.;

Superposed upon the gridiron D is the damper C, consisting of a sheet ofmetal pro vided with a series of rectangular openings, c, ofsubstantially the same size and shape and arrangement as the openings l)in the gridiron, and adapted to register with them. At each end of thegridiron and damper are two slots, 2) c', through which pass headedstuds A', projecting from the casing A. The length of the slots cgoverns the range of movement of the damper C.

To enable the gridiron B to be moved at will, a knob, D, is provided onthe outside of the casing, mounted on a short shaft, d, that passesthrough the gridiron B and carries on its inner end a disk, D. A slot,b2, in the gridiron permits the passage of the shaft (Z and allows thegridiron to move back and forth. The disk D carries a wrist-pin, d',which enters a curved slot, b3, formed in the gridiron B eccentric tothe shaft d. Upon turning the shaft d by means of the knob D, the pin dcauses the gridiron to move. An index, e, traveling over a graduatedscale, E, enables the gridiron to be set at any desired point in therange of movement', which is equal to one-h alf the width of one of theopenings b.

The damper C is arranged to be moved automatically by the followingmeans: Fast i ened to the inside of the casing A is one end of athermostatic bar, F, composed of two strips of dissimilar metal-such asbrass and steek-having unequal rates of expansion under heat. The stripsare riveted lirmly together, and to the free end of the bar thus vformedis secureda jaw, G, in which is pivoted one end of aV link, l-I,connecting the jaw with one arm of a bell-crank lever, I, fulcrumed onthe stud A. The other arm of the lever is forked, and engages with apin, K, projecting from the damper C. lVhen the bar j 'E is expanded byheat, its free end moves down, owing to the greater expansion of theupper strip of metal. This movement is comniunieat-ed to the lever I,and causes the damper to slide toward the right in Fig. 2. The openingsl) c in the gridiron and damper are so related that when both are attheir eX- treme left-hand position the openings will not register, butwhen at their extreme right-hand i position the openings will register.Further- IOO more, when the damper C is in its extreme l lett-handposit-ion the gridiron B can be shifted to either limit o'l' itsmovement without opening a passage through the damper. New, when thegridiron and damper are both at the left hand it requires ybut amoderate degree ol:` heat to expand the bar F enough to fully open. thedamper, thereby admitting cool air to .relieve the temperature of theoven. It, however, the gridiron .l is set at the righthand limit, itwill require a considerable expansion of the bar to open the damper,since the damper must slide a greater distance toward the right in orderto cause the openings t) c to register; but since the gridiron B can beset at various intermediate positions it Afollows that the damper C canbe required to move to a greater or less distance from its extremeleft-hand position before the slots I) c will register. l'n this wav thedegree of heat required in the oven. can be closely regulated betweencertain extremes and the oven kept at a predetermined temperati'ire.

rlhe index e and scale E enable the gri diron B to be set at anvpointand indicate the tem* perature which exists inside the oven. It the ovenbecomes too hot, the damper gradually opens to admit cool air and`gradually closes as the temperature lowers 'toward the predeterminedpoint. It is obviousv that my improvement ean'be applied to automaticdampers of various kinds, and may be varied in dee tail. withoutdeparting Vfrom the spirit of the invention.

l am aware that it is not 'new to use an adj ustable gridiron with anautomatic damper, and that a piu engaging with a slot is an oldadjusting device. I do not claim an)v of these parts separately, butmerely in eomli ination, for the purpose set forth.

llaving thus described my invention, what l claim7 and desire to secureby Letters Patent, isM v The combination, with the casing A, having thestuds A and slots a, oli' the reciprocating gridiron l, having openingsb, straight slots b and if?, and eccentric slot Us, the shaft d,passing' through the slot U2, and carrying disk D provided with pin d',engaging with slot U", the reciprocating damper C, haring the openings cand superposed upon the gridirou '13, the th ermostatic bar li, an d tl1e bell-crank lever l, engaging with the damper C and coun ected withthe bar F, all combined and operating substantially as and Vforthepurpose set forth.

ln testimony whereolI l aliix in v signature in presence of twowitnesses.

GEORCrE HENRY CRO\\'ELL.

l'Vitnesscs:

R. i CHAMBERLIN, VALENTINE GRAY.

